A benefit to doing it this way is that you can see if there is any rotten plywood that needs to be replaced before installing the new roof.
How to install metal roof shingles.
Place a sheet from top to bottom on a section of the roof.
Nail the drip edge in place using your hammer and roofing nails.
Always install flashing around a chimney and other valleys where two roof planes meet as these areas are more prone to leaks if not protected.
Starter shingles should be laid at the drip edge nailed down with roofing nails.
This framework has three big advantages.
Next lay the shingles working from the lower corner of the roof upward.
Install metal roofing sheets.
Install new flashing metal flashing is often called drip edge along the bottom of the roof near your gutters.
Fasten the shingles to the roof using the nail clips designed specifically for metal shingles.
Use 1 4 inch metal wood screws to attach the metal sheets to the wood slat board base.
Install the roofing screws vertically along each rib in the panel.
Better steel shingle systems like the one shown install over a framework of 2x2s.
If you want to install steel over asphalt your best choice for installing metal roofing is to use a steel shingle system like the one shown instead of the more common and more expensive standing seam steel.
Experts recommend that you work diagonally and raising each row of shingles gradually.
In a standing seam roof long single panels run vertically all the way from the eave to the ridge.
You should start your metal shingles installation with half a shingle or in accordance with your metal shingles installation manual which should be system specific starting from the left of the starter flashing or gable.
First because the frame is screwed directly to the rafters and the interlocked shingles are screwed to the frame the roof can withstand winds of up to 120 mph without damage.
Be sure the larger edge is laid so that the small edge of the next panel will overlap it.